Integrated circuit (IC) devices, such as a power converter, a power supplier, and so on, use a pulse width modulation (PWM) controller. The pulse width modulation (PWM) controller includes an oscillator to secure a pulse signal having a variable frequency. For example, in a PWM controller utilizing a boundary conduction mode (BCM) control algorithm, it is important to prevent the PWM controller from entering a continuous conduction mode (CCM). To prevent the mode change of the PWM controller from a BCM to the CCM, the PWM controller includes an oscillator that performs an oscillation holding operation when the BCM of the PWM controller ends.